U.S. drinking water regulations tied to reduced arsenic exposure

(Reuters Health) - The public’s exposure to arsenic, a naturally occurring chemical element linked to cancer and birth defects, declined after U.S. regulators tightened restrictions on the amount of arsenic allowed in drinking water, a recent study suggests.

Arsenic is one of the most common elements in the Earth’s crust and a natural contaminant in water in many regions of the world. In 2006, the U.S. Environmental Protection Agency (EPA) reduced the amount of arsenic allowed in drinking water from 50 micrograms per liter (50 ug/L) to 10 ug/L.

For the study, researchers examined national health survey data collected from 2003 to 2014 on 14,127 adults as well as results of urine tests for arsenic exposure.

During the study period, average arsenic exposure for people using public drinking water regulated by the EPA declined 17 percent, from 3.01 ug/L to 2.49 ug/L, the study found. During that same period, there wasn’t a meaningful change in arsenic exposure for people using private well water, a source not regulated by the EPA.

“When people ingest arsenic from food or drinking water, arsenic gets distributed throughout the human body and affects nearly every major organ system,” said lead study author Anne Nigra, of Columbia University Mailman School of Public Health in New York.

Previous research linked the new EPA arsenic regulations to a decrease in violations over time, Nigra said by email. But before this study, it wasn’t clear whether fewer violations also meant lower arsenic exposure in the population.

The reduction in arsenic for public water users could translate into anywhere from 200 to 900 fewer cases of lung and bladder cancer each year, as well as 50 fewer cases of skin cancer annually, the researchers estimate in The Lancet Public Health.

“Arsenic is a potent carcinogen that causes lung, bladder and skin cancers,” Nigra said. “It is also associated with cardiovascular disease, impaired cognitive development in children and adverse birth outcomes.”

Roughly 70 percent of the participants in the study used public water systems, however many southwestern cities’ public water supplies come from sources with naturally occurring arsenic levels above the maximum allowed by the EPA, including Los Angeles, Albuquerque, Scottsdale and Tucson.

Private wells, meanwhile, are the main source of drinking water for roughly 45.5 million Americans, researchers note. There is wide variation in arsenic levels from private wells.

While researchers did account for other common sources of arsenic exposure in foods and tobacco products, the study wasn’t a controlled experiment designed to prove whether or how the new EPA rules directly affected exposure to the element in drinking water.

Even so, the results offer fresh evidence of the potential for water regulations to prevent diseases associated with arsenic exposure, said Dr. Philip Landrigan, author of an accompanying editorial and a researcher at the Icahn School of Medicine at Mount Sinai in New York.

“Contrary to some of the things that EPA officials have said in recent weeks, arsenic is a proven carcinogen and any dose carries a risk of cancer,” Landrigan said in a telephone interview.

For people getting water from private wells, it’s worth testing the water for bacteria as well as arsenic and other chemicals, Landrigan advised. But it’s hard to clean water to remove chemicals, especially when arsenic is naturally occurring in the soil.

“The best thing people can do at that point is stop drinking water from the well,” Landrigan said.

The good news with arsenic is that it’s cleared from the body a few days after people stop drinking contaminated water, said senior study author Dr. Ana Navas-Acien, also of the Mailman School of Public Health.

“However, a research question that remains open is whether past arsenic exposure, even in the absence of current exposure, can still induce adverse health effects,” Navas-Acien said by email. “For that reason, preventing arsenic exposure in the first place is critical.”